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| Year : 2012 | Volume
: 5
| Issue : 3 | Page : 233-237 |
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| Utility of admission physiology in the surgical triage of isolated ballistic battlefield torso trauma |
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Jonathan J Morrison1, Euan J Dickson2, Jan O Jansen3, Mark J Midwinter1
1 Academic Department of Military Surgery and Trauma, Royal Centre for Defence Medicine, Birmingham Research Park, Vincent Drive, Edgbaston, Birmingham B15 2SQ, United Kingdom
2 Department of General Surgery, Glasgow Royal Infirmary, 84-108 Castle Street, Glasgow G4 0SF, United Kingdom
3 Surgical Department, 144 Parachute Medical Squadron, 16 Air Assault Medical Regiment, Royal Army Medical Corps, Cholchester, Essex, CO2 7UT, United Kingdom
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| Date of Submission | 22-Jun-2011 |
| Date of Acceptance | 07-Sep-2011 |
| Date of Web Publication | 14-Aug-2012 |
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 Abstract | | |
Background: An assessment of hemodynamic stability is central to surgical decision-making in the management of battlefield ballistic torso trauma (BBTT). Aims: To analyse the utility of admission physiological parameters in characterising hemodynamic stability. Settings and Design: A retrospective analysis of consecutive admissions, with BBTT, to forward surgical facility in Afghanistan. Materials and Methods: The cohorts' admission physiology, need for operative intervention, and mortality data were collected retrospectively. The cohort was divided into patients requiring surgery for Life-Threatening Torso Hemorrhage (LTTH) and those not requiring immediate surgery (non-LTTH). Statistical Analysis: Parameters were compared using two sample t tests, Mann-Whitney, Fisher's exact, and Chi-square tests. Receiver operator characteristic curves were used to identify significant parameters and determine optimum cut-off values. Results: A total of 103 patients with isolated BBTT were identified: 44 in the LTTH group and 59 in the non-LTTH group. The mean New Injury Severity Score ± Standard Deviation (NISS±SD) was 28±14 and 13±12, respectively. The heart rate, systolic blood pressure (SBP), pulse pressure, shock index (SI=heart rate/SBP) and base excess were analysed. SI correlated best with the need for surgical torso hemorrhage control, P<0.05. An optimal cut-off of 0.9 was identified, producing a positive and negative predictive value of 81% and 82%, respectively. Conclusions: Shock index (SI) is a useful parameter for helping military surgeons triage BBTT, identifying patients requiring operative torso hemorrhage control. SI performance requires a normal physiological response to hypovolemia, and thus should always be considered in clinical context. Keywords: Battlefield torso trauma, shock index, trauma surgery, triage
How to cite this article:
Morrison JJ, Dickson EJ, Jansen JO, Midwinter MJ. Utility of admission physiology in the surgical triage of isolated ballistic battlefield torso trauma. J Emerg Trauma Shock 2012;5:233-7 |
How to cite this URL:
Morrison JJ, Dickson EJ, Jansen JO, Midwinter MJ. Utility of admission physiology in the surgical triage of isolated ballistic battlefield torso trauma. J Emerg Trauma Shock [serial online] 2012 [cited 2021 Apr 23];5:233-7. Available from: https://www.onlinejets.org/text.asp?2012/5/3/233/99690 |
| Introduction | |  |
The assessment of ballistic torso trauma includes an early assessment of hemodynamic stability to identify life-threatening hemorrhage and stratifying the need for surgery or further investigation. [1] "Stability" thus features strongly in most trauma algorithms, but it is a nebulous concept, the assessment of which combines objective physiological parameters and subjective clinical measures, coupled with clinical experience. Robust definitions for the same are lacking.
The management of battlefield ballistic torso trauma (BBTT) is currently undergoing a similar evolution to that of civilian practice in recent decades. Following the availability of field portable computed tomography (CT) scanning in mature facilities, not all patients with BBTT require operative intervention. [2],[3],[4] Stable patients can be investigated further, and a proportion may be selected for non-operative management (SNOM), supported by close observation in critical care facilities.
Management decisions tend to be more straightforward when patients are either profoundly unstable or clearly stable. The greater difficulty is in the hemodynamic paradox of "not-unstable, but not stable" middle group that constitutes the bulk of patients. We postulate that initial cardiovascular and acid-base parameters may be helpful in the identification and surgical triage of torso hemorrhage. The a priori determined parameters to be analysed are heart rate (HR), systolic blood pressure (SBP), pulse pressure (PP = systolic - diastolic blood pressure), shock index (SI = HR/SBP), and base excess (BE).
| Materials and Methods | | |
BBTT was defined as any penetrating injury between the clavicle and pubic symphysis following wounding by fragmentation (FGW) or Gunshot (GSW). All patients with BBTT admitted to the UK forward surgical facility in Afghanistan [North atlantic treaty organization (NATO) classification: Role 2], between October 2007 and September 2008, severe enough to require torso CT, laparotomy, or thoracotomy were included. Patients were identified from a prospectively maintained CT and operation theatre log and their notes retrieved with the approval of the local Caldicott Guardian. Data were collected retrospectively onto an Excel spreadsheet and included the first recorded observations (HR and BP), BE from arterial blood gas analysis, CT scan findings, operative intervention, injury pattern, transfusion requirement, and 28-day mortality. Patients in cardiac arrest and those with serious extra-torso injury defined as a peripheral vascular injury, traumatic amputation, or head injury were excluded. The reason for excluding patients with associated injuries is that it introduces an extra-torso source of hypovolemia, thus compounding the analysis.
Several scoring systems were also generated to enable the comparison of admission physiology, injury pattern, and predicted survival in a validated way. The revised trauma score (RTS) was used to report physiology, which is a composite score of respiratory rate, blood pressure, and conscious level and is inversely proportional to survival. [5] The new injury severity score (NISS) was used to report anatomical injury severity using the abbreviated injury scoring where a higher score represents greater injury. [6] The RTS and NISS can be combined using trauma injury severity score (TRISS) methodology to calculate percentage predicted survival. [7]
The BBTT cohort was divided into two groups: The life-threatening torso hemorrhage (LTTH) group included all patients who underwent immediate surgery for hemorrhage control from solid organ injury, massive hemothorax, pelvic fracture, failed SNOM, or torso vascular injury. Patients who did not require immediate intervention for hemorrhage were termed as the non-LTTH (non-LTTH) group, consisting of patients with no evidence of peritoneal violation on CT, hemothorax managed by chest drainage only, solid organ injury selected for successful non-operative management or non-therapeutic laparotomy/thoracotomy. [Figure 1] is a flow chart explaining patient selection.
Statistical analysis
Statistical analyses were performed using two sample t tests, Mann-Whitney, Fisher's exact and Chi-square tests. Receiver operator characteristic (ROC) curves and decision plots were used to choose significant parameters and determine optimum cut-off values. Analysis was performed using Minitab 15 statistical software (Minitab Inc, Pennsylvania, USA) and P<0.05 was considered significant.
| Results | | |
Over a 12-month period, there were 615 consecutive admissions with combat-related injury, of which 122 had sustained BBTT as defined in the methods. A CT scan of the torso was used to direct management in 50 patients. Exclusions included 6 patients without a central pulse and 13 with severe associated injuries leaving a cohort of 103 patients. The LTTH group consisted of 44 patients undergoing: 31 laparotomies, 4 thoracotomies, 9 thoraco-laparotomies, including two failures of SNOM. All patients requiring immediate surgery underwent concomitant damage control resuscitation (DCR). The non-LTTH group consisted of 59 patients undergoing: 20 laparotomies for hollow organ injury, 9 non-therapeutic laparotomies (NTL), 1 non-therapeutic thoracotomy, and 27 patients who underwent successful SNOM. [Table 1] describes the demographic, admission physiology, injury severity, and mortality data of the groups. | Table 1: Demographic data, admission hemoglobin, transfusion requirements, shock index, injury severity, and mortality of patients with ballistic battlefield torso trauma
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Patients in the LTTH group had a lower admission hemoglobin and higher transfusion requirement than patients in the non-LTTH group [Table 1]. There was also a statistically significant difference between cardiovascular parameters, base excess injury severity scores, and mortality of the two groups. A binary logistic regression was performed to calculate the probability of life-threatening torso hemorrhage for SI, HR, SBP, PP, and base excess. The strength of association was calculated using Pearson's correlation, expressed as a P value. A ROC curve was then plotted and the area under the curve (AUC) calculated. [Table 2] describes the findings.
The SI was identified as having a statistically significant correlation and a ROC curve had an AUC of 0.85. [Figure 2] illustrates the ROC curve for SI. In order to identify a suitable cut-off point, a decision plot of predictive value against SI was drawn, which identified 0.9 as the best trade-off between positive and negative predictive values. The decision plot is shown in [Figure 3]. | Figure 2: The Receiver operator characteristic curve for Shock Index predicting torso hemorrhage
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Using a SI cut-off of 0.9, the positive and negative predictive values were 81% and 82%, respectively, with a sensitivity and specificity of 75% and 86%, respectively. Of the 11 patients with a SI <0.9 who did require operative intervention (ie, false negative results), there was a mix of solid organ injuries in 10 patients, with no injury grade above 3. The remaining patients had sustained a GSW involving the common iliac vein and appeared to be inappropriately bradycardiac at 60 bpm for an SBP of 75 mm Hg, suggesting a peri-arrest rhythm. This patient was the only fatality in the false negative group, and died in the intensive care unit (ICU) due to multi-organ failure on post-operative day 1.
Of the 10 NTLs in the LTTH group, 4 were on suspicion of hollow organ injury following CT scanning and the remaining 6 had an SI of <0.9 and had not undergone CT scanning. SNOM was attempted in 29 patients, with two failures who had indices of 1.14 and 1.11. All patients successfully managed non-operatively had an SI of <0.9. One patient had an SI of 0.53, who underwent a non-therapeutic thoracotomy (NTT) for a minor pulmonary contusion for a GSW to the chest.
Within the cohort, 35 patients had sustained hemothoraces, managed operatively in 13 cases, with 1 NTT as discussed above. Patients with an SI >0.9 were more likely to require a thoracotomy (9/17 vs 2/18), P=0.01 using Fisher's exact test.
There were 10 (10%) fatalities, with 3 patients presenting with indices <0.9. One patient is the one discussed above and the remaining two had a liver and mesenteric vascular injury, both associated with multiple hollow organ perforations. Both patients died in ICU on their third post-operative day of sepsis. Of the 5 patients who died due to bleeding within 24 h of admission, all had SI of >1.1.
| Discussion | | |
This study is a retrospective analysis of a consecutive series of patients with isolated BBTT. From an analysis of the patients' admission SI, HR, SBP, PP, and BE, we identified SI as the most predictive of torso hemorrhage. Using a cut-off of 0.9, we have demonstrated its ability to discriminate significantly between patients requiring immediate operative intervention for torso hemorrhage or further investigation. In this cohort, had an SI threshold been used to direct patients to either operation or CT, potentially 7 non-therapeutic interventions may have been prevented. Applying the same threshold to the management of hemothoraces, patients with an SI <0.9 are unlikely to require a thoracotomy.
The major disadvantage of this study is that the retrospective design may not have identified all eligible patients and their management was non-protocolized. However, by the manner in which the data were collected, it is unlikely that any serious injury will have been missed and the non-protocolized management does not affect the outcomes used in this study. Unfortunately, the cohort was not sufficiently large to include a validation cohort.
The use of SI as a measure of cardiovascular performance has developed due to the unreliable nature of isolated blood pressure and HR measurements in identifying hypovolemic shock, [8] except at extreme ranges. [9] The use of SI in the identification of hypovolemia is not a new concept, [10] but has been eclipsed by other more sophisticated scoring systems. [11] SI has been shown to correlate with cardiac index in animal models of hypovolemia [12] as well as, clinically, in patients in sepsis [13] and hemorrhagic [14] shock.
In recent times, there has been a resurgence of interest in the use of SI in trauma as a predictor of mortality and in field triage due to its ease of calculation. [15],[16] Most publications use mortality as an end point, reporting optimum sensitivity and specificity between 0.8 and 0.9. [14],[17] The only study analysing SI in torso trauma found a statistically significantly difference between survivors and non-survivors (mean SI values of 1.27 vs 1.65), although APACHE II scores and admission lactate were found to be more significant in predicting mortality. [11]
A strength of SI appears to be in the ability to identify relatively normotensive patients who have occult hypoperfusion and will go on to require intervention such as massive transfusion. [16],[18] This makes it ideal for surgical triage where management decisions generally surround the difficult hemodynamic paradox of "not unstable, but not stable".
The use of SNOM on the battlefield does raise the issue of the safe length of time to observe patients prior to aeromedical repatriation. This was not an issue in this series, as all patients who underwent aeromedical evacuation had undergone operative intervention, thereby reducing the risk of occult injury becoming symptomatic in flight. All patients managed conservatively were local national patients who were discharged into their local healthcare system for continued care. This issue will require future consensus, but is beyond the scope of this current study.
There are a number of caveats surrounding the use of the SI as its performance is dependent on a "normal" physiological response to hypovolemia. As noted by the patient who presented in a peri-arrest rhythm following a torso vascular injury, an inappropriate bradycardia with hypotension for whatever cause (eg, decompensation or beta blockade) will give a falsely reassuring low value. One would hope that the clinical picture would dictate otherwise.
An additional concern is the effect of aging on the cardiovascular response to hypovolemia. [19],[20] This has been examined by a study of 13,657 patients aged <55 years and 2,420 patients aged ≥55 years [20] by using SI to predict 48-h mortality. ROC curves were used to identify a cut-off of 0.83 in younger patients and 1.0 in older patients. The latter was further refined by multiplying the SI by the patient's age, a value of greater than 50 indicating a significant risk of death. Undoubtedly, a contributing factor to our significant results is the fact our population (age±SD: 24±13) is fairly homogeneous. However, it is important to note that only 10% of our population were military, and therefore 90% of our cohort had not been medically screened.
| Conclusion | | |
Admission SI is a sensitive and specific physiological parameter in assisting military surgeons triage BBTT, identifying patients requiring surgery for LTTH. SI performance requires a normal physiological response to hypovolemia, and thus should always be considered in clinical context. Further investigation is required in a bigger population, with a wider range of physiological reserve, injured by a mixture of traumatic etiologies.
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Correspondence Address:
Jonathan J Morrison
Academic Department of Military Surgery and Trauma, Royal Centre for Defence Medicine, Birmingham Research Park, Vincent Drive, Edgbaston, Birmingham B15 2SQ
United Kingdom
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0974-2700.99690
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2] |
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